Antibiotics of cephalosporin series are widely used in therapy for treatment of diseases which are caused by general pathogenic bacteria in mammals including human beings. There have been numerous studies aimed at increasing the efficacy and stability of the antibiotics of cephalosporin series, resulting in the development of various cephalosporin compounds.
For example, U.S. Pat. No. DES. 2,702,501 discloses various cephalosporin derivatives, including autibiotic known as cefotaxime, having a quaternary ammoniomethyl group in 3-position and/or 2-(2-aminothiazol-4-yl)-2-hydroxy (or substituted hydroxy) iminoacetamido group in the 7-position of cephem nucleus.
Among these known cephalosporin antibiotics, a compound known as ceftazidime, which is disclosed in DE U.S. Pat. No. 2,921,316 displays superior antibacterial activities against Gram-negative bacteria such as Pseudomonas aeruginosa, while it exhibits relatively inferior antibacterial activities against Gram-positive bacteria, in particular, Staphylococcus species. On the contrary, cefotaxime has been reported to have antibacterial activities against Staphylococcus species, while it possesses less effective antibacterial activities against Pseudomonas aeruginosa.
Accordingly, there have ensued further efforts to develop cephalosporin compounds having an excellent activity of broad spectrum, e.g., against both Gram-positive and Gram-negative bacteria including Pseudomonas aeruginosa.
For example, European Patent Application No. 47,977 discloses cephalosporin compounds having the following formula(A): ##STR2## wherein: n is 0 or 1;
Am is an optionally substituted amino group; PA1 B is a thiadiazolyl group (which is attached to its neighbor group via its two carbon atoms); PA1 R.sup.a is a hydrogen or a cycloalkyl, optionally substituted alkyl or carbamoyl group; and PA1 R.sup.b is an optionally substituted thiazolium or pyrazolium, tri(lower)alkyl ammonium, or pyridinium group having the formula of ##STR3## wherein: R.sup.c is an (lower)alkyl substituted with cycloalkyl, methyl, hydroxy, alkoxy, halogen, cyano, carbamoyl, carboxy or sulfonyl, (lower)alkenyl or (lower)alkylthio optionally substituted with carboxy, amino optionally monosubstituted by (lower)alkyl, (lower)alkanoyl or aminobenzenesulfonyl, di(lower)alkylamino, carbamoyl substituted with (lower)alkyl, hydroxy(lower)alkyl, (lower)alkoxy, hydroxy or cyano, di(lower)alkylcarbamoyl, thiocarbamoyl, cycloalkyl, phenyl, hydroxy, (lower)alkoxy, halogen, (lower)alkoxycarbonyl, (lower)alkanoyloxy, (lower)alkanoyl, carboxy, sulfocyano, nitro or hydroxysulfo(lower)alkyl group; PA1 R.sup.d is a hydrogen or a carbamoyl or the same as R.sup.c ; and PA1 R.sup.e is a hydrogen or the same as R.sup.c. PA1 R.sup.2, R.sup.3, R.sup.4, R.sup.5, R.sup.6 and R.sup.7 are independently a hydrogen or halogen or a C.sub.1-3 alkyl, amino or hydroxy C.sub.1-3 alkylthio, cyano, carbamoyl, carboxyl, hydroxy C.sub.1-3 alkyl, nitro, acetyl or formyl group; and PA1 Q is CH, N or CCl. PA1 R.sup.8 is a C.sub.1-4 alkyl group. PA1 n is 0 or 1, PA1 Z.sup.1 is a hydrogen or an amino protecting group, PA1 Z.sup.2 is a carboxy protecting group, and PA1 X.sup.1 and X.sup.2 are independently a leaving group or a halogen atom.
However, search for the desirable antibiotics with The broad spectrum is far from complete.